摘要
豫西地区发育大量加里东期的花岗岩,研究这些花岗岩对于了解二郎坪岩群和北秦岭的构造演化具有重要的意义。通过对豫西青岗坪地区侵入二郎坪岩群的花岗闪长岩进行全岩地球化学、锆石U-Pb测年和Hf同位素的综合分析,取得以下初步认识:豫西青岗坪地区花岗闪长岩的形成年龄为475.2Ma±2.7Ma,此年龄限定了二郎坪岩群构造侵位的上限。豫西青岗坪花岗闪长岩具有较低的MgO、Fe2O3、Cr、Ni含量和相对较低的Mg#值,这些地球化学特征表明豫西青岗坪花岗闪长岩应为加厚下地壳部分熔融的产物。结合已有的资料,认为在古生代早期(520～480Ma)北秦岭地区发生了较大规模的陆壳汇聚碰撞,导致下地壳的缩短、叠置,豫西青岗坪花岗闪长岩便是这一俯冲叠置下地壳部分熔融的产物。
Caledonian granitoids are well developed in western Henan Province.The study of these granites is of great significance for understanding the Erlangping Rock Group and the orogenic process of the North Qinling orogen.This paper presents zircon geochronologic data,zircon Hf isotopic and related whole-rock geochemical analyses of a typical granitoid pluton in Qingangping area of western Henan Province,and gives the following results and understanding： The Qinggangping granitoid pluton in western Henan Province has a crystallization age of 475.2±2.7 Ma.This age can be used to constrain the emplacement time of Erlangping ophiolite.The Qinggangping granitoids have relatively low MgO,Fe2O3,Cr and Ni content and Mg number.These geochemical characteristics show that the granitoid should be the product of a thickened lower crust by partial melting.It can also be concluded that convergence-collision probably occurred in North Qinling in Early Paleoproterozoic period.
出处
《地质通报》
CAS
CSCD
北大核心
2012年第6期884-895,共12页
Geological Bulletin of China
基金
国家重点基础研究发展计划项目<陆壳超深俯冲和折返的岩石学记录>(编号:2009CB825003)
